1. Technical Field
The present disclosure relates to a reception device, etc. that receive a multiplexed signal and derive a plurality of data series from the multiplexed signal.
2. Description of the Related Art
A multiplexing scheme utilizing superposition coding is known as a scheme to multiplex and send a plurality of data series (see Seokhyun YOON and Donghee KIM, Performance of Superposition Coded Broadcast/Unicast Service Overlay System, IEICE Transactions on Communications, vol. E91-B, No. 9). Other known multiplexing schemes include time division multiplexing and frequency division multiplexing (see Thomas M. Cover, Broadcast Channels, IEEE Transactions on Information Theory, vol. IT-18, No. 1).
Compared to time division multiplexing and frequency division multiplexing, the multiplexing scheme utilizing superposition coding is suited to multiplexing a plurality of data series that are required to have different levels of noise tolerance (receiver tolerance). The multiplexing scheme utilizing superposition coding is also termed as layer division multiplexing. The multiplexing scheme utilizing superposition coding applied to multiple access is also known as non-orthogonal division multiple access (NOMA).
In the multiplexing scheme utilizing superposition coding, a transmission device superposes a plurality of modulated symbols, which are obtained by modulating each of a plurality of data series, using predetermined power allocation, and transmits the superposed modulated symbols. A reception device sequentially demodulates the modulated symbols that are multiplexed by superposition coding, starting with modulated symbols in a layer with high noise tolerance until the completion of demodulating modulated symbols in a layer to which a desired data series belongs.
More specifically, the reception device demodulates the modulated symbols in a layer with the highest noise tolerance to estimate a data series. When a desired data series is yet to be estimated, the reception device generates a replica of each modulated symbol from another data series that has been estimated to cancel the replica from the received signal, and demodulates modulated symbols in a layer with the second highest noise tolerance to estimate another data series. The reception device repeats these processes until the desired data series is estimated.